The present invention relates to a plate-type heat exchanger, particularly to a brazed-plate heat exchanger.
Such heat exchangers are used for example to reheat or vaporize oxygen or oxygen-rich fluid, particularly in air separation plants. An oxygen-rich fluid is defined as one having a number of O2 molecules with respect to the total number of molecules greater than 20% when the fluid is under pressure at least equal to 20 bar, and greater than 50% at lower fluid pressures, particularly greater than 60%.
Such heat exchangers may be used for distilling gas, air or hydrocarbons and more particularly still in a double air distillation column.
The body of a vaporizer-condenser consists of a stack of a great many vertical rectangular plates, all identical. Inserted between these plates are, on the one hand, peripheral sealing bars, and on the other hand corrugated spacers or fins, namely heat exchange corrugations with a vertical main orientation and distribution corrugations with a horizontal main orientation.
Other exchangers for which the invention is intended, are, for example, the main heat exchangers of pump equipment or any other plate-type heat exchanger, which vaporize oxygen under pressure.
In general, the corrugated spacers are obtained from thin sheet, typically of between 0.15 and 0.60 mm thick, bent, cut or stamped in a press or using other suitable tools.
Oxygen vaporizers are a place where fuels heavier than oxygen, such as hydrocarbons, particularly C2H2 present in small quantities in the atmospheric air like to concentrate. Combustions in the liquid oxygen can occur by accident in such vaporizers. It has been found that these combustions could have the effect of producing at least local explosions. In accidents of this type, it has been found that thin fins, particularly fins made of aluminium, were very vulnerable to combustion whereas the dividing plates were not. It was found that the dividing plates therefore made it possible to prevent the fire from propagating.
Such problems may also manifest themselves in the vaporization circuits of an exchange line.
A main object of the invention is to produce plate-type heat exchangers able to resist possible ignition phenomena, particularly ones intended for use in the treatment of oxygen-rich fluids, in which exchangers the costs of manufacture are not appreciably increased and the performance in terms of pressure drop and exchange of heat is not appreciably lessened.